1. Field of the Invention
The present invention relates to a method of casting a synthetic body and more particularly to a method of casting a write head for an ink jet printer having micro channels extending therethrough.
2. Prior Art
Ink jet printers employ write heads having micro channels extending through the head and terminating at nozzles, from which the ink emerges during printing as a jet or as individual droplets. Depending on the type of pressure with which the ink is supplied to the nozzle, such printing heads are characterized as operating at high-pressure, low-pressure, or under-pressure. When the high and low-pressure methods are employed, only a single nozzle is employed and the jet which emerges from the nozzle is electrostatically or magnetically deflected for formation of a character. When the under-pressure method is employed, a pressure less than atmospheric is normally maintained at the nozzle.
When an ink droplet is to be ejected, the pressure in the nozzle is briefly increased by means of a shock wave. Because the end of the nozzles remain unwetted in the under-pressure method, many nozzles can be disposed in tight proximity so that a deflection of the ink droplets becomes superfluous. For example, the nozzle openings may be arranged in two opposite rows of six openings each. All characters can be formed by selective excitation of the individual nozzles, i.e., ink droplets being ejected from selected nozzles at any given time.
In the past, the synthetic print head body with the micro channels employed with the under-pressure method, has been manufactured by means of casting or injection molding, with mold needles corresponding to the micro channels positioned such that their points are disposed in an arrangement corresponding to the grid of the nozzle openings. This needle arrangement is maintained, for example, by means of positive-lock centering of the needles in a metal sub-mold. Since the sub-mold accepts the frontal plane of the discharge openings of the micro channels, the position or attitude of the mold needles cannot be observed or measured, and automation of the molding operation becomes greatly impeded.
In addition, the previous method required is of a complicated displacement casting method, with a special casting mold which required substantial maintenance and cleaning.
It is therefore desirable to provide a method in which the molding of the print head can be automated, and in which precise positioning of the mold needles can be verified while at the same time maintaining favorable conditions for casting.